Does your masters team have a lot of triathetes on it or is it mainly those who are just swimming for fun or those who are competing at an older age in swimming? If there are enough who do triathlons perhaps you could suggest an open water day in the pool. They could take out the lanes and have you all practice simulated open water swimming. It's still not quite the same but there are several "drills" out there on the internet that can be implemented in the pool for this.
Ok, so you might have heard all of what I am about to say, but this is what I find helpful for me when I do openwater swimming (which has been ALL of my races so far):
What I found helpful, even if you are trying to place, is to position yourself to the outside of the pack (not necessarily to the back though). This will keep you from being kicked as much or jostled as much as you enter the water. I am not an age-grouper as I race in the athena division, but I do race to place in athena so I attempt to position myself somewhere strategically. I find that middle of the pack on the outside has given me plenty of room to get into the water at my own pace and then find my rhythm once I'm there.
Run into the water high knee style until you reach knee height then shallow dive in and start swimming (even if others have not!!) if you wait too long you will slow yourself down. I've also found that once I've found my rhythm swimming early on the race that there are many who have not and that, right there, gives me an advantage. I then move myself toward the middle of the pack and then to the buoys where I stay tight to the buoy line so I'm not way out in the open water causing me to swim a farther distance than necessary.
Something else that might be causing a little anxiety too (which did for me when I first started in open water) was the inability to actually see in the water. I practiced a little in the pool by closing my eyes and swimming (I read this in a book somewhere, this was not my idea). It did actually work...I got used to swimming several strokes and then sighting where I was going when I took my head out of the water.
Last, but not least, is just to get used to doing it. I was pretty bad (no really really bad) the first time I did it. Then it got better and better. Now I am OK at entering the water with others. I'm not great, but it's something I expect to do at races and I know what I need to do in order to make myself more comfortable (see above). Oh, also, if I can get my foot in the water before the gun goes off I feel better (as in I'm not running from dry ground)...I don't know why, but it just feels better to start from there;)
Hope some of this helps;) Good luck on all of your races! And fantastic job on getting so close to placing!! You will get there for sure!!

Awesome tips! Im doing my first Tri this weekend, and have done plenty of open water swimming, but havent done the whole "jump into the lake with a bunch of other people" thing yet. Hopefully it goes well!